Fuse indicator



FUSE INDICATOR Filed March 6, 1959 70 14 ly ql @4 4. as I 526 m w. c.LINTON 2,206,783

Patented July 2, 1940 UNETED STATES FUSE INDICATOR William C. Linton,Washington, D. C., assignor.

to Fuse Indicator Corporation, Washington, D. #0., a corporation ofDelaware Application March 6,

3 Claims.

The present invention relates to indicators which visibly point out thepower ratings and integrity of electrical fuses, having amongst itsprincipal objects to provide a casing for such indicators which may beeconomically constructed and the parts thereof easily and readilyassembled without the aid of additional fastening elements, therebyrendering the same commercially desirable.

Other objects of the invention will be in part obvious and in partpointed out hereinafter.

In order that the invention and its mode of operation may be readilyunderstood by persons skilled in the art, I have in the accompanyingdrawing and in the detailed following description based thereupon, setout an embodiment of the same.

In the drawing:

Fig. l is a vertical section through a plug fuse embodying the presentinvention.

Fig. 2 is a bottom plan view of the cover section of the indicatorcasing.

Fig. 3 is a top plan view of the body portion of the casing.

Fig. 4 is a vertical section through the cover of the casing.

Fig. 5 is a vertical section through the body portion of the casing.

Fig. 6 is a vertical section through an indicator attachment forcartridge type fuses.

Fig. '7 is a detailed vertical section through the cover of theindicator attachment.

Fig. 8 is a detailed vertical section through the base portion of theindicator attachment, and

Fig. 9 is a vertical section taken on the line 9-9 of Fig. 6 in thedirection of the arrow points.

Referring now more particularly to Figs. 1 to 5 inclusive of thedrawing, I have illustrated a plug type fuse consisting of a base Ihaving a tubular extension 2 and an annular flange 4 formed therewith.An. explosive chamber 3 is formed within this base and attached theretois a rivet or central contact terminal 5. The fuse link 6 has one endconnected to the rivet 5 i and is supported by the tubular extension 2of the base. The casing for housing the explosive chamber and fuse link5 has a tubular wall 1 which rests upon the annular flange 4 of the baseand is connected to the latter by means of the threaded contact shell 8.The opposite end of the fuse link 6 is also connected to the contactterminal 8 and should this fuse link become blown or ruptured, thepressure of the given off would tend to separate the base I 1939, SerialNo. 260,158 (01. 200- 121) and the cover in order that the gases mayescape therebetwcen and around the shell 8.

The casing for the fuse is divided into an upper'or cover section 9 anda lower section Ill.

The cover section 9 has a recess H formed in the lower face'thereof,whereas, the outer. face of the section it has a companion recess l2formed therein so that when the sections 9 and is are together, theywill house a. glow lamp I3 111- the manner as is best illustrated inFig. 1 of the drawing. This glow lamp has the lead wires M and 15connected thereto and a leak resistance I6 is arranged between thesections of the lead wire l5. This leak resistance 15 is preferably madefrom a plastic composition containing a suitable conductive material anda binder, which latter will adhere to metals whereby when the lead wiresI l and I5 are embedded therein, these Wires will be electrically andmechanically connected to the resistance. The lead s wire Hi extendsthrough a vertical opening ll formed within the body portion of thesection It and itsouter extremity is connected to the threaded contactshell 8'. A portion of the lead wire l5 and the leak resistance [5arranged therein is seated within the recess l8 also formed within theupper face of the section IU of the casing from where the lead wire I5extends through a vertical opening l9 also formed in this section In,and this lead wire l5, after extending through a slot formed within thetubular portion of the base I, is connected to the central contactterminal or rivet 5.

The lower face of the cover 9 is provided With one 'or more recesses 2|which receive corresponding knobs or projections 22 formed with theupper face of the section ID of the cover. The lower face 23 of thecover and the outer face 210i the base ID are subjected to polishing,resulting in a highly and brilliantly polished surface.

' From the above arrangement, it will be obvious that the fuse link 6 isconnected in series with the terminals 5 and 8 and that the lamp [3 andthe leak resistance I6 are also connected in series with the terminals 5and '8 but in parallel to the fuse link 6, whereby, should this fuselink become blown or ruptured, electrical current will pass through theconductors l4 and I5 for causing the lamp 13 to glow and in thismanner,-indicate the integrity of the fuse link 6.

' In Figs. 6 to 9, inclusive, I have illustrated an indicator attachmentfor cartridge type fuses which consists of a sectional casing comprisinga-lower or base section and an upper or cover section 26. These sectionshave companion recesses 27 and 28 formed therein so that the glow lampl3 may be completely housed within the casing of the indicator. A recess30 is also formed within the base section 25 of the casing for receivingthe resistor l6 and the cover section 30 is provided with knobs orprojections 3| capable of being seated within aligning recesses formedwithin the base 25 in the manner as best shown in Fig. 9 of the drawing.Prongs or similar fastening members 32 may be connected to the casing ofthe indicator whereby the latter may be not only attached to a cartridgetype fuse but may be electrically connected to the terminals of the fusewhereby electrical energy may be supplied from the terminals of the fusethrough the members 32 to the lead wires 14 and 15 of the glow lamp.

The base I of the plug fuse and the base sections It and 25 of theindicator casings may all be molded from suitable molding powder toprovide an insulator having the required tensile strength and dielectricqualities whereas the top or cover sections 9 and 26 of the indicatorcasings are made from thermo-plastic molding powders which produce atransparent or translucent cover for the lamp [3 whereby the rays oflight therefrom may project through this cover. The thermo-plasticmolding powder preferred for producing these covers is a polymerizedmethyl methacrylate which is available in a wide variety of brillianttranslucent colors and which may be molded in the shape and designs asherein shown, through ordinary molding processes which require heat andpressure. The sections l and 25 of the casing may also be made fromthermoplastic molding powders but when prepared from thermo-settingmaterials, the upper part should have mixed therewith a thermo-plasticmolding powder similar to the molding powder used in casting the covers9 and 26, in order that when a cover is placed upon the lower or basesection of the casing, it may be cemented thereto by a cement containinga solvent which will render plastic the adjacent faces of the coversections and base sections of the casings, whereby, the two will becemented to one piece, thereby eliminating the necessity of additionalfastening elements or other means for permanently connecting the coversto the base sections of the casings.

When using polymerized methyl methacrylate and thermo-plastic moldingpowder, the cement used for connecting the sections of the casingtogether should be one containing a solvent of the lower ketone andester solvents, and mixtures of aromatic hydrocarbons with small amountsof alcohol. By highly and brilliantly polishing the surfaces 23 and 24of the sections of the casing, the joints between the two will be hardlynoticeable when the solvent contained within the cement used forconnecting these sections together completely evaporates. The jointsbetween these sections are mechanically as strong as the materialitself.

The cover sections of the indicator housings may be of various colorsfor designating the power ratings of the fusible elements of the fuse towhich they are connected and when the lamp l3 glows, a brilliant lightwill be visible from the exterior or outer face of the fuse or fusecasing which extends entirely over the outer face of the translucentcover and is not confined to any particular point within the indicatorcasing. When these covers of the indicator casing are made of colors, acolored light corresponding with that of the color of the casing will beprojected from the fuse to which the indicator is attached for not onlyindicating the integrity of the fuse but also designating the particularpower rating of the blown fuse.

From the foregoing, it is apparent that the upper and lower sections ofthe indicator casing may be made of the same thermo-plastic moldingpowders so that when again heating the contacting surfaces 23 and 24 ofthe sections, they will become plastic. When these sections of thecasing are placed together and these plastic surfaces allowed to cool, awelded connection is established between the two sections, therebyeliminating the necessity of solvents, cements 0r fastening elements forconnecting the sections of the casing together. When the base sectionsIn or 25 of the indicator casings are prepared from thermo-settingplastic powders, it is necessary, during the molding of these powders,to sprinkle or otherwise place upon the outer face or the face 24 of thecasing H! a thermo-plastic molding powder which is cast with thethermo-setting molding powders. When heat or a solvent is applied to thethermoplastic material formed with the outer face 24 of the section illof the casing so as to render the thermo-plastic materials containedtherein again plastic, this surface will adhere to the plastic surface23 of the cover 9 should heat or a solvent be applied thereto.

Manifestly, the construction herein shown is capable of considerablemodification and such modifications as come within the scope of myclaims, I consider within the spirit of my invention.

I claim:

1. An indicator for fuses comprising a casing, said casing having arecess formed in the opened upper end thereof, contact terminals, a glowlamp seated within said recess and connected in series with said contactterminals, a cover having a recess formed in one face thereof forreceiving and housing said lamp, means for preventing the rotation ofsaid cover upon said casing and means for connecting the opposed facesof said cover and casing together.

2. The combination with a plug fuse having a base and a casing, contactterminals and a fuse link connected in series with said contactterminals, said casing having a recess formed therein and extendinghorizontally across the outer face thereof, a glow lamp indicator andleak resistor seated within said recess of the casing, said casinghaving openings formed therein each having one end communicating withsaid recess and their opposed ends communicating with said contactterminals, lead wires extending through said openings for connectingsaid glow lamp indicator and leak resistor in series with said contactterminals but in parallel to said fuse link and a cover connected tosaid casing for housing said glow lamp.

3. An indicating plug fuse comprising a base, a casing fitted to saidbase forming a combustion chamber therein, a central contact secured tosaid base, a threaded contact shell connecting said base and casing, afuse link arranged within said combustion chamber and connected inseries with said central contact and said threaded contact shell, saidcasing having a recess formed within the outer face thereof, a glow lampand resistor seated within said recess of the casing, said casing havinga pair of vertically extending openings formed therein, one end of eachof said said glow lamp and leak resistor in series with said centralcontact and said threaded contact shell but in parallel to said fuselink, a cover for housing said lamp and leak resistor seated upon theouter face of said casing and means 5 for connecting said cover to saidcasing.

WILLIAM C. LINTON.

